The field of protecting an individual's personal property as well as industrial/commercial real estate has mushroomed in the last 20 or 25 years from a multi-million to a multi-billion dollar industry. Initially, this industry concerned itself with protecting structures, such as homes or businesses from intrusion, particularly by thieves or other nefarious individuals. Generally, entry points to the particular structure, such as doors or windows were wired in a manner such as to produce a signal if the door or windows were opened without shutting off an alarm. Similarly, if a window is broken, an alarm would be emitted and/or transmitted to a remote location such as a police station or a monitoring agency.
Unfortunately, valuable personal property such as audio/visual components, computers and the like were provided with sensors such that if the item or personal property was either moved without permission or transported across a threshold, such as the perimeter of the individual's residence or place of business, an alarm would be sounded as well as alerting the police or the monitoring agency.
Additionally, during the last several years, we have witnessed an alarmingly large increase in the amount of domestic as well as international terrorism being perpetrated on innocent individuals. Although a large amount of time, effort and money has been budgeted for developing different devices, systems and methods of protecting both individuals as well as their personal property, this increase in terrorism has not abated. This is partly due to the fact that access control devices supervise access at perimeter doors, but fail to detect vandalism or terrorist threats to the exterior and the immediate vicinity of a structure or area to be protected.
Prior art security protection intrusion devices consist of a single wire cable attached to a fence or similar structure to sense vibration, noise or the actual cutting of the cable.
A number of U.S. patents have issued in the security field. For example, U.S. Pat. No. 4,213,122, issued to Rotman et al describes an intrusion detection system for protecting a metallic structure, such as an airplane, trailer, hangar or other metallic object or housing. The purpose of this patent was to secure the physical integrity of the metallic structures by detecting any attempts to penetrate through a zone or protection surrounding the metallic structures. As shown in FIGS. 1a and 1b, a radio frequency source 11, 21 would be connected to the particular metallic structure 10, 20 to be protected. The metallic structure would be surrounded by ground wires 12, 22 which in turn would be themselves surrounded by receiver wires 14, 24. The metallic structure becomes one part of a radiating antenna system producing electromagnetic fields in the surrounding receiving wires. These fields are monitored by radio frequency pickup devices which would detect any changes from a quiescent or undisturbed state. These changes would be produced by an individual crossing the receiving wires into the protective zone surrounding the metallic structures. However, as can be appreciated, directly connecting the radio frequency sources to the metallic structures could potentially cause problems to various electronic components provided in the metallic structures. Additionally, while the patent to Rotman et al would be able to sense a disturbance in the electromagnetic field surrounding the metallic structures, it would not be able to pinpoint the exact spot of this disturbance. This is particularly important when a rather large area is to be protected.
U.S. Pat. No. 4,588,988, issued to Karas describes a system for the protection of a particular secure area from intruders by sensing the deformation of a physical barrier surrounding the secure area, such as a barbed wire fence or fences shown in FIGS. 1 and 2. One or more ported coaxial cables are disposed in relation to the barbed wire fence or fences. Radio frequency sources would be connected to the coaxial cables and would be used as a source of radio frequency energy as well as for receiving reflection produced by disturbances of the electromagnetic field produced by an intruder. However, as was true with respect to the patent to Rotman et al, while the patent to Karas would sense the presence of an intruder, it could not make a determination of the exact point of entry of the intruder into the secured area. Additionally, since the radio frequencies are induced into barbed wire coils to produce the electromagnetic field, this particular configuration could not be utilized as a direct attachment to solid walls constructed from concrete, glass or brick. Even if the coaxial cables shown in the Karas patent were utilized in a manner to surround the secured area, as indicated previously, it would be ineffective to locate the point of intrusion.
U.S. Pat. No. 5,446,446 issued to Harman describes a device that uses a cable with a center conductor and one or two sense wires. Although this cable can detect the point of intrusion, it depends upon vibration and is best attached to a chain link fence. It is not effective on solid structures such as brick, block or concrete walls or similarly constructed buildings. Additionally, since this system operates on a sensed vibration, many false positive outputs could occur.